First Grow

Nute burn!!!! On one tip, of one leaf, of one plant. The research I've done on it says it seems to be a common rookie error so I dropped the feeding amount buy 50% today. The stems are thickening and getting harder and have about 4 sets of leaves on each plant. The LST on them have really started showing positive signs as you can see in the pics. But this is really two stories, one of the happy healthy plants I speak of above, then there's the story of Little Quazy. Im not too sure if she is still worth the effort but she seems happy and if anything will be a learning experience. Im struggling with heat in that there is too much change between the temp when lights are on and off. Maybe one of you legends have the answer. Has anyone used infrared reptile light to keep things toasty when the lights are of? Ive got the timer to go off at the hottest time of the day but we have days where it will have temps can drop to as low as 14 degrees. Really enjoying the grow process and Growdiaries.